1. Field of the Invention
The present invention relates to an intake control apparatus for an internal combustion engine, which comprises an electronically controlled throttle and a variable valve mechanism varying an opening characteristic of an intake valve, for controlling the electronically controlled throttle and the variable valve mechanism based on a target intake pressure and a target intake air amount, and a method thereof.
2. Description of the Related Art
Heretofore, there has been known an intake control apparatus for adjusting an intake air amount of an internal combustion engine by a valve timing control of an intake valve and also closing an electronically controlled throttle in the case where a negative pressure is required to be generated.
Further, Japanese Unexamined Patent Publication No. 2001-173470 discloses an apparatus for correcting closing timing of an intake valve according to a change in negative pressure by an opening control of an electronically controlled throttle.
In the above related art, a target volumetric flow ratio is corrected according to an intake pressure detected by a negative pressure sensor, and the closing timing of the intake valve is determined based on the corrected target volumetric flow ratio.
However, if the detection result indicates an abnormal value due to the failure of the negative pressure sensor or the intake pressure indicates an abnormal value due to the failure of the electronically controlled throttle or an influence by the valve deposit, the target volumetric flow ratio is erroneously corrected.
Then, if the target volumetric flow ratio is erroneously corrected, the control accuracy of the intake air amount is lowered, resulting in the degradation of drivability of the internal combustion engine.